Loudspeaker



Sept. 9, 1941. J. P. QUAM Re. 21,898

LOUDSPEAKER Original Filed April 5, 1935 2 Sheets-Sheet 1 4Z 4@ 19 v g5'37 /6 i v/Clg l l. vl l IWT-,

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LOUDSPEAKER original Filed April s, 1955 2 sheets-sheet :a

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Ressued Sept. 9, 1941 IJOUDSPEAKEB.

Juncal.Quam,Chicago.Ill..a|signol'toQuani-g Nichols Company, Chicago,Ill., a corporation of Missouri Original No. 2.124.338. dated July 19,1938. Serial No. 14,389. April 3, 1935. Application for reissue March10, 194i, Serial No. 382,597

23 Claims.

My invention relates in general to loudspeakers, and particularlyloudspeakers with the cone type diaphragm and a vibratory unit therefor,ordinarily known as a magnetic type speaker.

Dimculty is encountered in the present magnetic type loudspeakers inthat it is not possible to obtain the volume or the faithfulness ofreproduction over the4 entire band `of frequencies obtained from thedynamic type loudspeaker; Chattering and distortion often develop whenthe speaker is operated at high volumes so as to impair reproduction.

A further disadvantage to the present magnetic type speaker, incomparison with a dynamic speaker, is the fact that it is less sturdy,and has a shorter life. Furthermore, it does not lend itself to shipmentand handling as satisfactorily as the dynamic type.

It is an object of my invention to provide an improved magnetic type ofloudspeaker.

.A further object is to provide an improved vibratory unit for a conetype diaphragm loudspeaker.

It is also an object to provide a magnetic type loudspeaker which willfaithfully reproduce at large volume a radio broadcast oversubstantially the entire band of frequencies.

One ,of the features of my improved driving unit is the provision of alaminated permanent magnet comprising closed ring-shaped body members,in which said laminations are punched out on a punch press.

An additional feature is the provision of a pair of laminated polepieces adapted to carry a laminated amature and a field coiltherebetween, with the three elements designed to be mounted between thelaminations of the pennanent magnet, as a frame for the elements.

A further feature of my invention is the provision of a vibratory unitfor a loudspeaker which may be completely assembled and then quicklymounted directly on the usual frame support for the cone-shapeddiaphragm of the speaker.

It is also a feature of my invention to provide a vibratory unit inwhich substantially all of the parts maybe stamped out on a punch press,and then assembled with a very small amount of labor.

A still further feature is the provision of parts for the vibratory unitof such a nature that they may be shipped disassembled, and then readilyassembled at the point of use for the loudspeakers without anycomplicated assembly lines or highly trained operators.

Other objects and advantages of my invention will be apparent from thefollowing description' taken with the drawings, in which:

Fig. l is a front elevation of the completely assembled loudspeaker.

F18. 2 is a rear elevation thereof.

Fig. 3 is a fragmentary rear elevation partly in section of thevibratory or driving unit for the speaker.

Fig. 4 is a similar view to that of Fig. 3. showing in addition abi-part clamp for rigidly clamping the pole pieces outside the amature.

Fig. 5 is a sectional view of the driving unit along the lined-i of Fig.3. f

, Fig. 6 is af sectional view of driving unit as mounted on theconevhousing taken along the line I-l of Fig. 3.

' Fig. 'I i`s a sectional view of )he vibratory unit as mounted on thecone housing taken along the line 'I-l of Fig. 3.

Fig. 8 is a view of the driving unit, particularly the magnet, polepiece, armature and coil members.

Fig. 9 is a top elevation showing the manner in which the laminations ofthe pole pieces are stampedV out of a single strip of steel with aminimum of waste in the strip.

Fig, l0 illustrates a modification of the closing plate for thevibratory unit housing.

In practicing my invention I provide a loudspeaker having a cone-shapeddiaphragm supported on an annular frame, and a stylus extendingrearwardly from the center of the cone. I provide a vibratory unit forthe diaphragm to be mounted at the rear of the cone support and vcomprising a laminated permanent magnet including a plurality of closedring magnets serving as a frame and having a central aperture to carry apair of Y-shaped laminated pole pieces which in turn support a laminatedarmature and an encircling energizing coil intermediate said polepieces. A driving arm extends from within the armature to the stylus onthe diaphragm, and a non-magnetic housing is provided around the entiredriving unit when assembled on the cone support.

Referring now to the drawings, in the loudspeaker of my invention Iprovide the usual coneshaped diaphragm lli supported on the annular rimof a frame Il, having a pair of rearwardly protruding legs I! to carry aslotted mounting strip II. The strip Il is preferably welded to the legsI2 of the frame. A stylus Il is rigidly secured atthe apex of the coneto extend rearn wardly through the mounting strip.

In addition to obtaining marked improvement in the faithfulness ofreproduction and in the volume in the comercial embodiment of myspeaker, as contrasted to those of the prior art, I have simplified thedesign and assembly of the vibratory unit of my speaker so as tomaterially reduce the complete cost of the same. Both material and'laborcosts have been reduced by providing stamped parts readily assembled inthe vibratory unit. Furthermore, a very sturdy unit is provided. Invibratory units for loudspeakers in use at the present time, thepermanent magnet is of the horse-shoe type, forged from high carbonsteel at a relatively high cost. I provide a permanent magnet comprisinga pair of ring-shaped laminations I8 and stamped from a suitable magnetsteel preferably in the shape of a substantially oval ring with anelongated aperture in the center thereof. If I wish to increase thefield strength I may employ four, or even more laminations in thepermanent magnet, using an even-number so that they may be divided withan equal number on each side of the pole pieces as will be hereinafterdescribed. In a commercial embodiment I have stamped the laminatiom fromsteel strips or sheet steel M; inch thick in which the steel is softenough to permit stamping, but hard enough to provide they necessaryretentivity value. 'I'he individual laminations of the magnet areassembled as shown particularly in Figs. 6 and 'I to serve as a frame onthe inside and outside of a pair of Y-shaped laminated pole pieces I3and I9 including a plurality of laminations with extending legs 2| on anintegral tail piece 22. A pair of apertures 23 in the tail portion 22 ofeach of the laminations lof the pole Apieces provide holes the length ofthe pole pieces to receive fastening rivets 2li.

The individual laminations of theV pole piecesl I3 and I3 are preferablystamped from relatively thin silicon steel, and with the retainingrivets extending only through the tailportion of the laminations theremight be a tendency for the legs 2| to spread slightly in a longitudinaldirection. To overcome this difllculty I provide silicon steellaminations over the central portion indicated by the letter A and.steel laminations of greater thickness at each end as designated by theletter B. This assembly is also indicated by darker and lighter portionsin the pole pieces of Fig. 8. 'I'he steel laminations are of sumcientrigidity to prevent the longitudinal spreading oi' the legs of theintermediate silicon steel laminations when secured together bytherivets.

A laminated armature 24 is provided for mounting between the pole piecesand includes a thin knife-edge driving arm 2G having a right-angledextension 2l of the same area as the laminationsV for the armature, sothat the arm may be fitted into the center of the armature in thevertical plane of the stylus Il, to move as an integral portion of theamature. Apertures 23 are provided in each of the armature laminationsas well as in the extension 21 to receive retaining rivets to hold thelaminations of the amature together. A central aperture 2! is alsoprovided to receive a mounting spring 3| extending the entire lengththereof and protruding a -short distance from each end thereof. Themounting spring is preferably a phosphor bronze alloy, although othermaterials with the necessary ilexibllity and strength may also beemployed. The mounting spring must of course be stiff enough to insure afaithful movement in response to a variation in impulses applied, andstil! enough so that the amature .wont hit against the pole pieces invibrating.

As will be noted from a consideration of Figs 6 and 7, the armaturerocks about the mounting spring 3| as a central axis, although the onlytwisting of the spring that actually occurs is that between the portionsoldered to the armature and the torsion blocks, as will be hereinafterexplained. The mounting spring, of course, is rigidly soldered into thecentral aperture 29 so there is no relative movement as between thespring and the armature body itself at such soldered portion. Torsion ormounting blocks 32 of a non-magnetic metal iit over the ends of thespring 3| and are slightly spaced away from each end of the armaturebody itself to permit vibration of the armature itself, and spaced farenough away so that the block may be soldered to the end of the springwithout danger of soldering the block to the end laminations of thearmature. The torsion blocks are rigidly secured between the ends of thelegs 2| on the pole pieces and are initially alined by means of notchedportions 33 on each of the four corners of each of the blocks 32 tocorrespond with the ends of the legs 2|. The torsion blocks are of sucha size that when the armature is mounted between the pole pieces, an airgap 34 is provided between the armature and the ends of the pole piecespreferably of .005 inch. From the standpoint of sensitivityit is ofcourse important to keep this I as small as possible. However, I haveobtained satisfactory operation with an air gap varying from .004 to.007 inch for instance.

The channel between the legs 2| of the pole pieces is of such a size asto receive the frame of an energizing coil 36. 'I'he energizing coil hasa central elongated aperture wide enough to permit the insertion of thetorsionblocks 32 as shown particularly in Figs. 3 and 4 and preferablyof such a width that the projections on' the blocks will engage theinner insulating ring 35 on the coil whenrthe pole pieces, armature andcoil are clamped together. The energizing coil is wound with any desiredwire in the usual manner.

To assure a rigid assembly of the pole pieces, armature and energizingcoil, I employ a bipart spring clamp including a pair of clampingmembers 31 and 38 bent to engage the top of the tail portion of the polepieces at C and D and roundedout at the corners to remain out ofengagement'with mounting screws for the entire driving unit as will behereinafter described. The ,ends of the clamping members are bentoutwardly and apertured in the usual manner to receive bolts 33 ofnon-magnetic material and preferably brass. Upon tightening the clampbolts, the ends of the legs of the pole pieces engage the torsion blocksso tightly that there is no possibility of looseness or chattering withresultan-t loss in eiilciency in the speaker. The clamp also of coursereinforces the natural magnetic attraction between the two pole piecesof opposite polarity. Mechanically, this assembly of the torsion blocksrigidly secured between the pole pieces provides in effect a solidone-piece mounting for the armature. The armature is the only memberwhich can move, and as impulses v with.

A very rapid and simple assembly of the entire 'armature body.

unit is provided in nrst assembling the laminated pole pieces andlaminated armature with the driving arm therein. 'Ihe central aperture2l in the amature iomed by the various apertures in each of thelaminations is oi a diameter approximately therwidth o! the phosphorbronze mounting spring Il. This aperture is reamed out at itsendsRasshowninFig. litoadepthoiapproximately /4 inch. 'Ihe spring 8l isthen inserted into the aperture, a drop oi acid as iiux is placedintheaperture,andthearmaturedippedintoa solder bath to rigidly solderthe spring into the Any excess solder is wiped oi! and the torsionblocks I! are iitted over the ends of the spring. spaced away from thelaminations of the amature. The springs are then soldered to the blockon the outside thereof. After the field coil Si is inserted between thelegs o! the pole pieces the amature is placed in the central aperture ofthe coil and properly alined by' means of the alining notches Il. Theclamp is then positioned and drawn up to a tight engagement around thepole pieces. A iig is employed for aligning the elements of theassembly.

To prevent dust, dirt or moisture from getting into the driving unit, Iprovide a non-magnetic housing Il including a closed cap l2 and a bottommember 4I. To complete the assembly of the' vibratory unit, the motorassembly comprising the pole piece, amature, and coil, clamped togetherby the bi-part clamp, is positioned between the two laminations it andIl oi the permanent magnet with the shoulders M on the pole piecesiitting into the alining notches Il in the laminations. The cap l! isthen placed over this assembly and the bottom member 4I properlypositioned, after which this assembly is mounted on the molmting stripIl by bolts I1. A pair of bolts Il are inserted through the neccessaryapertures in the lower portion of the assembly to hold the members ofthe permanent magnet together over the pole pieces and close the housingover the entire driving unit. In the meantime the split end li of thedriving arm has been placed over the stylusv Il and when solderedthereto completes the assembly of the driving unit on the cone support.Suitable wire leads l! extend from the i'leld coil 3l to be soldered tomounting posts ll eyeletted onto the mounting strip Il. Lead wires Ilthen extend from the eyelets to the radio receiver.

Inasmuch as dirt and moisture, collecting in the air gap would impairthe operating eillciency, it is very desirable to employ the cap l! andbottom plate Il to house the unit. It is understood, however, that thevibratory unit may, if preferred, be mounted directly on the conesupport with the bolts l1 and 4l as described.

A modiiication of the bottom member of the` housing is illustrated inFig. 10. wherein a liber insulating strip It is assembled in the samemanner as the member Il. I also utilize the member v the remaining partsofthe vibratory unit, an inexpensive unit is provided, and at the sametime averysturdyone. Thevariouspartsoitheunit are very simple, and dueto their design may be lt as a terminal strip by eyeletting a pair oi'terminal lugs i1 thereon. The wire leads I2 are brought to the eyeletsand soldered thereto, and the wire leads Il from the receiver aresoldered onto the terminal lugs l1, thus eliminating the lugs il.

To further protect the vibratory unit against moisture and dirt whenemploying a housing, I slit a piece of thin surgical rubber Il and slipit over the driving am before the unit is placed against the bottommember oi the housing. This ei'i'ectively closes the aperture l! in thebottom member through which the arm extends.

very readily assembled. It is possible to ship the unit disassembled toits place oi use, and there to be very quickly and cheaply assembled..The vibratory unit is exceedingly sturdy and capable of long andemcient use.- In the commercial embodiment o! the invention I obtainmarked improvement in reproduction over the entire frequency range, anda large increase in volume over the magnetic type speakers in use at thepresent time.

A Although I have described my invention in its preferred embodiments,it is understood that I am not limited thereby, but limit the inventiononly by the scope oi the appended claims.

1. A vibratory unit for a magnetic speaker; including a motor assemblyhaving a pair of pole pieces. an armature supported ior oscillatoryvibration between the polepieces and having a driving member inconnection therewith, means 'for retaining said pole pieces and amaturein ture vassembly engaging the pole pieces, and of such a size and shapeas to extend considerably beyond the edge of the assembly in oppositedirections, and positioned at right angles to the line oi' 'movement ofsaid drivingmember to serve as a mounting frame i'or the pole pieceamature assembly.

2. A vibratory unit for a loudspeaker comprising a motor assemblyincluding a pair of oppositely disposed pole pieces, an amature mountedfor ,oscillatory vibration between said pole pieces in a manner to forman air gap therebetween, said amature having mounting means in abutmentwith the active faces of said pole pieces, a spring clamp engaging theoutside edge of each of the pole pieces to draw the pole pieces towardthe amature, to maintain said armature in ilxed mounting positiontherebetween, and a permanent magnet mounted on said motor assembly asan assembling trame therefor.

3. A vibratory unit for a loudspeaker including a pair oi oppositelypositioned Y-shaped pole pieces each having a pair of forwardlyextending legs with a channel therebetween, a tail portion extendingrearwardly from the channel and of the same size as said channel, anenergizing coil carried in the oppositely positioned channels, anamature supported between the pole pieces and within the ield coil, apermanent magnet comprising a plurality of ring-shaped members with amember resting on one side of each pole piece tail, and another memberresting on the other side of each pole piece tail.

4. A vibratory unit for a loudspeaker comprising a permanent magnet, avibrating armature, a laminated pole piece on each of two sides of saidarmature, each o! said pole pieces comprising a plurality of relativelythin Y-shaped laminations having a pair of forwardly extending legsdefining a channel therebetween and a tall piece extending rearwardlyfrom the leg portion and of substantially the same size as said channel,a retaining rivet through said tail pieces, and means i'or preventing alongitudinal spread f of the pole piece at the leg portions, said meanscomprising relatively heavy laminations assembled at each end of therelatively light lamination assembly with said heavy laminations havinggreater rigidity than Asaid relatively light laminations.

5. A loudspeaker motor including an armature, a spindle rigidly securedto said armature, holders carrying said spindle and positioned adjacentto said amature but being slightly wider than said armature, a pair ofVpole pieces having their active faces bearing against opposite side.; ofsaid holders and accurately spaced by said holders to permit operationof the armature therein, and means for supporting said pole pieces andsupplying magneticflux thereto.

6. A loudspeaker motor including an armature, separate pole piecespositioned on opposite sides of said armature with end faces toward saidamature, and a centrally apertured ring-shaped permanent magnet engaginga side face at right angles to an end face of each of said pole pieceswhereby it may firmly engage both of said pole pieces irrespective oftheir exact dimensions and nt in the vertical direction through the twopole pieces and armature, said pole pieces being laminated, and meansbeing provided for clamping all of the laminations of the pole piecesagainst said magnet to insure their proper vertical alinement.

'7. A vibratory unit for a loudspeaker including a pair of oppositelypositioned laminated pole pieces, each including a plurality of Y-shaped laminations with a pair of forwardly extending legs having achannel therebetween and a tail portion extending rearwardly from thechannel, an energizing coil, and an armature supported between the polepieces, and a ringshaped permanent magnet in engagement with the polepieces on the tail portion thereof.

8. In a vibratory unit for a loudspeaker, an armature unit comprisingapair of spaced apart non-magnetic stationary torsion blocks, asupporting spring rigidly secured at its ends at the blocks, an armaturemember rigidly secured on said spring with the latter extending throughthe longitudinal center of the member from end to end, said membercomprising a plurality of laminations with a one-piece diaphragm drivingelement positioned insaid member intermediate the ends thereof andhaving a body portion conforming in shape precisely to the laminationsin said member, with an integral elongated driving arm, fiat and of thesame thickness as the body portion extending away from said body portionin said armature and at right angles thereto for connection with thediaphragm.

9. A vibratory unit for a loudspeaker including a vibratory armaturecomprising a plurality of apertured laminations, a diaphragm drivingmember having an apertured body portion conforming in shape to saidlaminations and positioned corresponding 'thereto in said armatureintermediate the ends thereof and a knife-edge elongated driving armextending away from the body portion in the plane of said body portionand integral therewith, and a mounting spring for the armature extendingthrough the aperture in each lamination and the aperture in the bodyportion of the driving member, with said mounting spring being rigidover at least a portion thereof with respect to the laminations anddriving member.

10. A vibratory unit for a loudspeaker including a pair of oppositelypositioned Y-shaped polepieces each having a pair of forward legs and atail portion, an apertured energizing coil carried in the recess formedby the legs oi' the pole-pieces, an armature in the aperture of Ithecoil having supporting means carried by the pole pieces, and anapertured permanent magnet carried on a corresponding face of each ofthe -tail portions with a portion of each pole-piece extending into themagnety aperture.

11. A vibratory unit for a loudspeaker including a pair of Y-shapedblock-like pole-pieces, each having a pair of forwardly extending legsand a tail portion, with said pole-pieces positioned with the legsfacing ea'ch other, an energizing coil carried in the oppositelydisposed recesses in the pole-pieces formed by the legs, and an armaturewithin the energizing coil having a stationary carrying plate at eachend supported by the active faces of the pole-pieces, and a closedsubstantially oval shaped permanent magnet resting on a correspondingside of each of the tail portions of the pole-pieces, with acorresponding forward leg of each pole-piece lying in the aperture ofthe magnet and acting with the magnet to position the pole-pieces withrespect to one another and the armature plate therebetween.

12. A vibratory unit for a loudspeaker including an apertured plate-likepermanent magnet, a vibratory armature, and a pair of block-like Y-shaped pole-pieces supporting the armature therebetween, each pole-piecehaving a recess on at least one side of the tail portion correspondingin depth substantially to the thickness of the permanent magnet with therecesses on corresponding sides of the two tail portions, and saidpermanent magnet lying on the .t'ail portions at the correspondingrecesses with theforward leg on said recess side of each pole-piecepositioned in the magnet aperture.

'13. A vibratory unit for a loudspeaker including a pair of spaced apartpole-pieces with the active face of each pole-piece oppositely disposedfrom the other, a pair of spaced apart non-magnetic plates between theactive faces of the pole-pieces and supported solely by engagement withsaid faces, a block-like armature between said pole-- pieces` and saidplates, a spindle irremovably secured to said plates and extendingthrough the armature in the longitudinal axis thereof to support thesame for vibratory movement, and a permanent magnet resting upon acorresponding outside face of each pole-piece with such outside faces atright angles to the active faces of the pole-pieces, and said magnetacting to position said pole-piece-armature assembly elements withrespect to one another and acting as a mounting frame for the vibratoryunit.

14. A vibratory unit for a loudspeaker comprising a pair of oppositelydisposed single unit pole-pieces, a laminated armature mounted betweenthe pole-pieces for oscillatory vibration, means for supporting saidarmature comprising a stationary torsion block at each end thereofretained between the pole-pieces in engagement with the active facesthereof, a mounting spring irremovably secured at each end in a torsionblock and extending through the armature in the longitudinal axisthereof in a line at right angles to the line of movement of thediaphragm of the loudspeaker.

15. An electromagnetic loudspeaker motor including a continuous ovalshaped permanent magnet having an elongated central aperture, a pair ofopposed pole-pieces positioned against one face of the magnet with eachpole-piece having a portion extending into the aperture of the magnetto. position said pole-pieces with respect to said magnet, and a clamparound the polepieces on an outside face of each at right angles to themagnet engaging face to draw the po1e` pieces toward one another.

16. An electromagnetic loudspeaker motor having a pair of opposedpole-pieces, an armature unit retained bythe pole-pieces between theactive faces thereof. a permanent magnet for the pole-pieces, and aspring clamp around said polepieces engaging an outside face of eachparallel to the active face of that pole-piece and adapted to beadlustably tightened to draw the polepieces toward one another torigidly retainthe amature unit therebetween.

1'?. Aloudspeaker motor including an armature, a spindle rigidly securedto said armature, apertured holders carrying said spindle in theapertures thereof and positioned adjacent to said armature but beingslightly wider than said armature, a pair of pole pieces having theiractive faces bearing against opposite sides of said holders and withsaid faces accurately spaced by said holders to permit operation of thearmature therebetween, and with said armature being spaced withreference to said pole faces to form an air gap therebetween and saidspacing being maintained as a result of said armature spindle beingcarried by said holders and said holders spacing said faces, and meansfor supporting said pole pieces and supplying magnetic flux thereto.

18. A loudspeaker motor including an armature, a spindle rigidly securedto said armature and serving as an axis therefor in the vibratorymovement of the armature, holders carrying said spindle and positionedadjacent to said armature but being slightly wider than said armature, apair of pole pieces having their active faces bearing against oppositesides of said holders and accurately spaced by said holders whereby tobe spaced relative to said armature to provide air gaps between saidarmature and pole faces and permit operation of the armature therein, acoil unit including insulating means extending around said armature andsaid holders but spaced from said armature with the holders preventingsaid insulating means from engaging the armature, and means forsupporting said pole pieces and supplying magnetic ux thereto.

i9. A vibratory unit for a loudspeaker comprising a pair of opposltelydisposed pole-'pieces each having a pole face thereon, a laminatedarmature mounted between the pole-faces for oscillatory vibration, meansfor supporting said armature comprising a stationary torsion block ateach end thereof retained between said faces of the pole-piecesinengagement therewith, a mounting spring irremovably secured at each endin a torsion block and extending through the armature in thelongitudinal axis thereof in a line at right angles to the line ofmovement of the diaphragm of the loudspeaker, with said torsion blocksalone determining the spacing between said pole faces and likewisedetermining the air `gap between the amature and pole faces.

20.` An electromagnetic loudspeaker motor having a pair of opposedpole-pieces, an armature unit retained by the pole-pieces between theactive faces'thereof, a permanent magnet for the pole-pieces, and springclamp means for said pole-pieces including a pair of members with eachmember engaging an outside face of each pole piece parallel to theactive face of that polepiece, and means operatively connected to eachmember and adjustable to provide relative movement therebetween to drawthe pole-pieces toward one another to rigidly retain the armature unittherebetween.

21. An electromagnetic loudspeaker motor having a pair ofV opposedpole-pieces, an arma- .ture unit retained by the pole-pieces between theactive faces thereof including an armature and armature supporting meansat each end of said armature positioned between the active pole faces todetermine the spacing between the active faces and the spacing betweenthe armature and each adjacent active pole face, a permanent magnet forthe pole-pieces, and a clamp around said pole-pieces including a pair ofmembers with each member engaging an outside face of each pole pieceparallel to the active face of that polepiece, and means to move onemember relative to the other to adjustably tighten the clamp and drawthe pole-pieces toward one anotherto rigidly retain the armature unittherebetween.

22. A vibratory unit for a loudspeaker including in combination a pairof oppositely disposed single unit pole-pieces, each `pole piece havinga pair of legs with a channel therebetween and an active pole face atthe bottom of the legs, a laminated armature positioned between theactive pole faces having driving means for the loudspeaker thereon, andmeans for supporting said armature in such position comprising astationary torsion block at each end of said armature retained betweenthe pole pieces, and each torsion block having oppositely disposedrecessed portions engaging the corresponding active pole faces and anextension between each two 'ref cessed portions extending into thecorresponding pole-piece channel, and a mounting spring irremovablysecuredat each end in a torsion block and extending through the armaturein the longitudinal axis thereof in a line at right angles to the lineof movement of the driving means on the armature.

, 23. A loudspeaker motor including a movable armature, a spindlerigidly secured to said armature, holders carrying said spindle andpositioned adjacent to said armature but being slightly wider than saidarmature, an energizing coil surrounding said armature and holders andmaintained out of physical contact with said movable armature by thewidth of said holders, a pair of pole pieces having active faces bearingagainst opposite sides of said holders and spaced apart accurately andsolely by said holders to permit operation of the armature therebetween,and means for supporting said pole pieces and supplying magnetic fluxthereto.

JAMES P. QUAI.

